Put benchmark config inside its execution

[ctubbsii]

• Configuration outside of the execution will apply to all executions of exec-maven-plugin when the profile is active, even executions that have nothing to do with the benchmark, so the benchmark-specific configuration should be contained inside the execution element
• Remove extra character from README

[ctubbsii]

For what it's worth, there is an exec-maven-plugin goal called "java" that is supposed to make it easy to run a mainClass without having to pass the -cp argument, but it doesn't correctly pass along the current project's classpath in a convenient way when it forks to execute the mainClass. It's frustrating, but calling exec:exec this way with the classpath as an argument to the java command is the easiest workaround.